Use of starch ether layers in diffusion transfer processes



United States Patent 3,203,796 USE OF STARCH ETHER LAYERS IN DIFFUSION TRANSFER PROCESSES Johan Lodewijk Verelst, Deurne-Antwerp, and Jose Therese Lemmerling, Edegem, Belgium, assignors to Gevaert Photo-Producten N.V., Mortsel, Belgium, a Belgian company No Drawing. Filed Apr. 27, 1962, Ser. No. 193,046 4 Claims. (Cl. 9629) The present invention relates to an improved photographic material for application of the silver complex difiusion transfer process and to a process for the manufacture and the use of this material.

' The principle of the silver complex diffusion transfer process is described in (U.S.P. 2,352,014) British patent specifications 614,155 and 654,630, and the German patent specification 887,733, wherein a light-sensitive material and a separate image receiving layer are used.

In the British patent specification 654,631 this process has been simplified by using a multilayer material which comprises essentially a support onto which consecutively the image receiving layer and the light sensitive layer are coated. The first layer contains developing nuclei and substances capable of forming such developing nuclei. The binding agent for this layer is hardened in such a way that its firmness in warm water and in solutions of alkali is assured. The second layer consists of a silver halide emulsion the binding agent of which has not been hardened so that this layer can be removed by dissolving.

After image-wise exposure of this material and its development in a developing solution containing a solvent for silver halide, a silver salt image which becomes visible after the emulsion layer of the material is washed away, is obtained in the image receiving layer. It appeared, however, in practice that a selective hardening of two adjacent gelatin layers can diflicultly be efiected on account of the ditfusion of the hardener whereby the washing away of the emulsion layers meets with some difficulties.

As an improvement thereto a thin intermediate layer, e.g., of starch, is applied between the emulsion layer and the image receiving layer. Such material however shows another disadvantage namely the sometimes early getting loose of the emulsion layer in the developing bath instead of in the rinsing bath.

It has now been found to obtain an excellent multilayer material used for the application of the silver complex difiusion transfer process, the silver halide emulsion layer of which can very easily be removed after treatment in the developing bath, by applying a thin layer, mainly consisting of an ether of a polysaccharide having a pyranose ring structure, e.g., a starch ether, between the image receiving layer and the silver halide emulsion layer.

As image receiving layer in a multilayer material according to the invention the support itself or a separate image receiving layer which is coated onto a support can be used. Such a separate image receiving layer is mostly prepared from colloid binding agents which are insoluble in cold alkali such as gelatin, mixtures of gelatin and sodium alginate, gelatin and carboxymethyl cellulose, polyvinyl alcohol, partially saponified polyvinyl acetate, cellulose acetate, hydrated colloidal silica, etc.

Developing nuclei or substances capable of forming developing nuclei in situ can be incorporated into the support which is used as image receiving material, into the separate image receiving layer and/ or in the support of this latter. Other substances such as developers, complexing agents, developing activators, stabilizers, black toning agents, etc. which are necessary for obtaining a difiusion transfer image or an improved difiusion transfer image in a multilayer material can be incorporated into these dilferent materials.

Ethers of polysaccharides having a pyranose ring structure which are suitable for being used in a material according to the invention will for convenience sake be identified in the further description as polysaccharide ethers. Suitable are i.a. derivatives of starch in which one or more hydroxyl groups are etherified with organic compounds such as methyl alcohol, ethyl alcohol, propyl alcohol. Hydroxyalkyl ethers and carboxyalkyl ethers of starch are also suitable. Groups which are considered are for instance: O-CH COOH, O-CH CH OH,

The thin layer of polysaccharide ether can be coated from a solution of at least one polysaccharide ether in aqueous alcohol with a concentration usually varying between 1 and 15% according to the applied coating method.

The polysaccharide ether coating composition can also contain besides the polysaccharide ether still other addings but in relatively small amounts such as gelatin, polyvinyl alcohol, cellulose ethers, cellulose esters and also aqueous dispersions of polyacrylonitrile, polyvinyl chloride or other water-insoluble polymers or copolymers.

It is also possible to incorporate substances, which can be incorporated into the image receiving material and which are mentioned above, into this polysaccharide ether layer from which they difiuse to the image receiving material before or during the treatment in the developing bath.

As an appropriate silver halide emulsion for applying the new method, any silver halide emulsion can be used provided its exposed silver salt, during the diffusion transfer process, is rapidly enough developed and its unexposed silver salt is rapidly enough complexed, while its binding agent may be any hydrophilic colloid, such as gelatin, polyvinyl alcohol or a sodium salt of polystyrene sulfonic acid which can be prepared according to our Belgian patent specification 608,259.

It is also possible to apply a layer between the lightsensitive layer and the polysaccharide ether layer and/ or between the image receiving layer and the polysaccharide ether layer according to the Begian patent specifications 609,394 and 609,395.

After exposure the multilayer material according to the present invention can be developed in a developing solution which has the same composition as the usual developing solutions for silver complex diffusion transfer. It generally contains the necessary ingredients for the development of the exposed silver halide such as hydroquinone and 1-phenyl-3-pyrazolidone and occasionally a solvent for the undeveloped silver halide such as sodium thiosulfate, sodium thiocyanate or ammonia. It is, however, always possible, as described above, to incorporate substances, which are usually present in the developing bath, into the multilayer material itself.

The silver halide emulsion layer can be detached from the polysaccharide ether intermediate layer by bringing the image-wise exposed and developed multilayer material in a rinsing bath at room temperature or even at lower temperature whereby the silver halide emulsion detaches as a coherent membrane or by other processes such as stripping off after contact with a sheet of paper.

The image which is obtained in the image receiving layer consists of finely divided metallic silver or silver compounds which are very reactive and hence are easily submitted to any after-treatment, used in the photographic technique such as reinforcing, weakening, discoloring contact hardening, coloring, etc.

'1950: pp. 76-77 and 140; vol. II, 1951-1954: pp. 156- 157; vol. III, 1955-1958: pp. 24-36 and in the patent literature cited therein.

The following examples illustrate the present invention.

Example 1 A suspension of the following composition is prepared: Water cn1. 950 Gelatin g-.. 30 Sodium alginate g 0.1% aqueous suspension of colloidal silver sulfide cm. 5 aqueous formaldehyde cm. 2 Hostapon T cm. 1

Trade name for the sodium salt of oleyl methyl tannide, marketed by Farbwerke Hoechst, A.G., Frankfurt am Main Hoechst, Germany.

From this suspension a layer is coated onto a paper support of 90 g./sq. m. in such a way that the weight of the dried layer amounts to 2.5 g./sq. rn. Onto this layer a second layer is applied, starting from the following solution:

Hydroxyethyl starch g 10 Water cm. 1000 5% solution of the sodium salt of dioctyl sulfosuccinic acid a cm. 2

This solution is coated in such a way that 1 1. covers sq. m. of paper support. After drying an orthochromatic and contrasty silver bromide emulsion containing 13 g. of silver bromide and 36 g. of gelatin per kg. of emulsion is applied thereon in such a way that the finally obtained emulsion layer contains 2.4 g. of silver bromide per sq. m.

After image-wise exposure the thus prepared reversal material is developed in a bath of the following composition:

G. Sodium sulfite (anhydrous) 80 Hydroquinone 34 'Potassium bromide 7 Sodium hydroxide Sodium thiosnlfate 20 Water up to 1000 cm.

Next the treated reversal material is brought into rinsing water so that the emulsion layer can be removed without mechanical means as a coherent membrane from the image receiving layer. layer a positive image of the original is obtained.

Water up to 700 cm.

'.1.rademark for a sodium salt of diisobutyl naphthalene sulfonlc acid of Badische Anilin- & Soda-Fabrik A.G., Ludwlgshafen (Rhine), Germany.

This suspension is coated onto a paper support of 90 g./sq. m. in such a way that the weight of the thus formed layer, when dried, amounts to 5 g./sq. m. Onto this first layer a second layer is applied from an identical solution of hydroxyethyl starch as described in Example 1. After drying a silver bromide emulsion is In the nuclei containing thus coated thereon that the finally formed emulsion layer contains 3.5 g. of silver bromide per sq. m. The silver bromide emulsion has the following composition:

800 parts of a photographic silver bromide emulsion with very vigorous gradation which contains 78 g. of silver bromide and 80 g. of gelatin per kg. of emulsion,

parts of a 25% aqueous solution of polystyrene sulfonic acid sodium salt (PI-IE7) with low molecular weight,

73 parts of ethanol,

7 parts of 1% aqueous solution of Sandozol (trade name for sulfonated castor oil of Sandoz A.G., Basel, Switzerland).

After image-wise exposure this prepared reversal material is developed in a bath of the following composition:

G. Sodium sulfite 50 Hydroquinone 10 Monomethyl-p-aminophenol sulfate 3 Sodium thiosnlfate 10 Potassium bromide 1 Trisodium phosphate 60 Water up to 1000 cm.

Then the treated reversal material is brought into rinsing water so that the emulsion layer detaches and decomposes into small flakes without mechanical means. Even at temperatures less than 10 C. the emulsion layer detaches easily. In the image receiving layer a positive image of the original is obtained.

Example 3 Example 1 is repeated using hydroxyethyl starch instead of hydroxypropyl starch.

We claim:

1. A method for obtaining an image according to the silver halide diffusion transfer process comprising the steps of image-wise exposing a multilayer material comprising successively a support, an image-receiving layer containing a member selected from the group consisting of development nuclei and substances capable of forming such nuclei, a layer essentially consisting of a starch ether and a light-sensitive silver halide emulsion layer, treating the exposed'multi-layer material in the presence of a silver halide complexing agent with a developing solution and bringing the thus treated multi-layer material in an aqueous rinsing bath so that the silver halide emulsion layer detaches as a coherent membrane.

2. The process of claim 1 further characterized in that said starch ether is a hydroxyalkyl starch.

3. The process of claim 2 further characterized in that said hydroxyalkyl starch is hydroxyethyl starch.

4. The process of claim 2 further characterized in that said hydroxyalkyl starch is hydroxypropyl starch.

References Cited by the Examiner UNITED STATES PATENTS 2,363,764 11/44 White 96-83 3,043,691 7/62 Weyde 9629 3,087,815 4/63 Ryan et al. 96-3 FOREIGN PATENTS 654,631 6/51 Great Britain.

706,333 3/54 Great Britain. 1,013,965 8/57 Germany. 1,055,953 4/59 Germany.

869,190 5/61 Great Britain.

OTHER REFERENCES Neblette, Photography-Its Materials and Process, Van Nostrand, New York, 5th Edition (1952), pp. 234-244.

NORMAN. G. TORCHIN, Primary Examiner. 

1. A METHOD FOR OBTAINING AN IMAGE ACCORDING TO THE SILVER HALIDE DIFFUSION TRANSFER PROCESS COMPRISING THE STEPS OF IMAGE-WISE EXPOSING A MULTILAYER MATERIAL COMPRISING SUCCESSIVELY A SUPPORT, AN IMAGE-RECEIVING LAYER CONTAINING A MEMBER SELECTED FROM THE GROUP CONSISTING OF DEVELOPMENT NUCLEI AND SUBSTANCES CAPABLE OF FORMING SUCH NUCLEI, A LAYER ESSENTIALLY CONSISTING OF A STARCH ETHER AND A LIGHT-SENSITIVE SILVER HALIDE EMULSION LAYER, TREATING THE EXPOSED MULTI-LAYER MATERIAL IN THE PRESENCE OF A SILVER HALIDE COMPLEXING AGENT WITH A DEVELOPING SOLUTION AND BRINGING THE THUS TREATED MULTI-LAYER MATERIAL IN AN AQUEOUS RINSING BATH SO THAT THE SILVER HALIDE EMULSION LAYER DETACHES AS A COHERENT MEMBRANE. 